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Originally Posted by Funfinder
Keeping all this in mind now we just need to know with what kind of radiation buried metal reacts in the most sensitive way.
This is not a question if 5kHz or 15kHz is better for ground penetration, it has to do with the reception systems we want to use.
One of them is the ion-chamber that seems to be extremly sensitive if well build, a second may be the electrostatic-receiver (we have to proof it first) and the third working is the "passive receiver" that seems to recognise a change of the electromagnetic energy of an area.
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Before you can decide what receiver you want to use, you must first define the signal you are trying to measure.
Defining the signal to measure implies you first know what signals exist in the location of buried metal.
Or alternately, you should know how signals sent to locations of buried metal react in a way that can be measured above the background noise.
To make it more clear, there are only two approaches to detecting buried metals:
1. A passive detector that detects signals existing in the area of buried metal. This kind may have active power elements inside it, but it is only designed to detect outside signals, not to transmit anything.
2. An active detector that sends out some kind of signal, then measures some kind of signal returning as a result of what it sent out. In this case the signal detected may be the same signal sent out which is changed in some way by the buried metal. Or it could be a different signal that appears as a result of the signal that is sent out. There are hundreds of examples that could apply to locating buried metals from either of these approaches.
Here are a few examples
- Passive detectors:
- Magnetometer - receives existing magnetic fields to detect buried metal.
- Passive gamma spectrometer scintillator - receives radiation from existing nuclides and measures them to detect when different metals are present.
- VLF mapping - receives existing VLF signals from distant transmitters and measures variations in the signal to detect metals.
- Dowsing - Is claimed to detect the location of buried metal from signal lines without sending out a signal.
- Active detectors:
- Conventional metal detector - Sends magnetic signal, detects secondary magnetic signal sent from location of buried metal.
- GPR - Sends radar signal - detects reflection from same signal to locate metal.
- Sonar - sends sound signal - detects reflection from same signal to locate metal under water, in air, and under ground in some unusual circumstances.
- Ground resistivity/Induced polarization - sends signal to ground, detects changes to signal sent to detect metals.
You can see why it is necessary to define what kind of signal your receiver is to detect before deciding what receiver to design, or how to optimize it to find the signal above the background noise.
But how can you choose what signal to detect?
We can look in the Remote Sensing forum for suggestions that have been given by people who claim to build working LRLs:
Some suggestions of signals to detect given by LRL builders:
- Static electric field anomaly in location of buried metal
- Magnetic field anomalies in location of buried metal
- Gold ions discharging in location of buried metal
- Infrared anomalies on surface of the ground in location of buried metal
- Mechanical (molecular level) vibration of gold in location of buried metal
- Voltage anomaly in the soil in location of buried metal
- Visible light emanating from the soil in location of buried metal
- Soil conductivity (or resistivity) anomaly in the soil in location of buried metal
- RF anomalies detected in transmitted signals when directed at location of buried metal
- Modulation anomalies to VHF reception detected when VLF source is directed at location of buried metal
- Modulation anomalies to VHF reception detected when pulsed IR light source is directed at location of buried metal
- Harmonic resonance augmentation of transmitted RF when antenna is directed at location of buried metal (Audio modulation frequency dependent)
These were some suggestions from LRL experimenters I have found from searches in the Remote Sensing forum.
When I actually asked what is the best signal to try to detect, I got very little response other than measure the voltage in the air,
and pressurized gas can come from a buried treasure location:
http://www.geotech1.com/forums/showthread.php?t=15605
Maybe you can think of a better signal to build metal detecting equipment for.
Best wishes,
J_P